I don't get the overreaction. If some stranger is walking around the neighborhood, doing something legal but suspicious or out-of-the-ordinary, a cop should have the right to stop him and ask questions. Cops should have the power to stop and ask questions when someone is doing something that is not normally done. Sure, he has the right to do things that are legal. But at the same time, cops should have the right to investigate. They weren't saying he did anything illegal.
[I am assuming there is not racial or religious profiling going on].
Photographing a famous public piece of artwork is "suspicious"? That's what a lot of us are reacting to.
Yes, I know the painting is on a natural gas tank. They should still let people photograph it; photographs can already be found on the Web, so the horse is pretty much out of the barn, as they say.
It's suspicious if it is not done frequently, and it is a sensitive location (e.g. a huge gas tank). Cops aren't stopping you if you take pictures of the Washington monument or the Statue of Liberty. But if something that doesn't happen normally happens, it's natural the the cops want to look into it.
Sure, the picture of the painted gas tank might be on the web, but a guy with a camera might be taking pictures of other sensitive things that are at the location, not just the painted gas tank.
Imagine, that every time you say "Hi" to some girl you get visited by her father and brother carrying baseball bats. Nothing illegal, they are just making sure your intentions are nice.
Would you like that?
[I am assuming there is not racial or religious profiling going on].